Inbound one-way audio — SDP codec answer diverges by backend stack (BYOC, +902168882917)

Support Help
1

Production-critical, ongoing since Sept 3→4 night. Already opened ticket #58155 (auto-ack only so far).

Symptom: caller hears complete silence on all inbound calls, agent hears/transcribes caller fine. Outbound unaffected.

Root cause from pcap_url on 10 calls: carrier SIP offer identical every time (RTP/AVP 8 0 18 101). When call enters via signaling IP 18.98.16.121, Retell answers with a single codec (RTP/AVP 0 101) — audio works. Since Sept 4, calls enter via .120/.123 and Retell answers with four codecs (RTP/AVP 0 8 9 101) — ambiguous negotiation, caller’s carrier drops mismatched RTP.

Working call: call_103196a07051d1993c37df131d6 (2026-09-03T18:22Z)
Broken call: call_c411843e8d47185b507cf6a6178 (2026-09-04T15:27Z)
Agent: agent_0b26275640e8519a44b12446b6

@Shah-Fazal — since you’re already looking at SIP traces on the 18.98.16.x pool today (Sone’s thread), could this be related? Appreciate any help, our customers can’t reach us by phone.

2

Hello @Maytras I’m checking this with the team and will get back to you as soon as I have an update.

Thank You

3

Hello @Maytras We have pushed a fix, please let me know if everything is working as expected.

Thank You

4

Hi @Shah-Fazal,

Confirmed — the fix is working. Just tested an inbound call and audio came through both ways. Thank you for the quick turnaround on this.